<p num="79">FIELD: measurement technology.</p> <p num="80">SUBSTANCE: invention relates to biometry and specifically to detection of weak magnetic fields of biological objects. Essence of the invention consists in the possibility of using a common for all sensors resonant radio-frequency (RF) field, having a constant frequency, or frequency-related to a magnetic field, measured by one or more sensors of the multichannel diagnostic system, providing dynamic compensation of shift of magnetic resonance line center (occurring in each sensor due to variations of local field and proportional to these variations), performed by closing feedback to control intensity of pumping light, and as a result – value of light shift of magnetic resonance line. Measurement of magnetic field variations is carried out by measuring variations of pumping power; in case of using low-frequency (0–100 Hz) intensity modulator (LCM – liquid crystal modulator), measurement of the value of magnetic field variations is carried out by measu